Stimulation systems and methods

ABSTRACT

Oil stimulation systems enable vibrations, including strong vibrations, to be transmitted towards the productive formation, via the rock matrix, from the exterior of a well casing with minimal attenuation from a component with a greater toughness than the contacted rock. In-situ amplification for the vibration transmission counters attenuation and stimulates oil flow within a productive formation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Canadian Patent Application No. 2,922,814 filed on Mar. 4, 2016, the disclosure of which is incorporated herein in its entirety.

FIELD OF THE INVENTION

The example embodiments presented herein relate to the recovery of hydrocarbons from a productive formation using a vibratory process. In several example embodiments, stimulation systems and methods generate vibrations and transmit the said vibrations to the rock matrix from the exterior of the well casing.

BACKGROUND OF THE INVENTION

The oil flow stimulation effect in a hydrocarbon impregnated rock matrix subjected to a vibratory process is well known and is the subject of extensive research. Despite being explored for decades, the stimulation typology using vibrations to improve the oil recovery has not yet achieved large scale use in actual practice.

A reason for this absence of such extended application is linked to the problem that vibrations based stimulation methods failed to deliver upon the target area the critical amount of energy able to trigger a considerable production enhancement.

This absence of effect magnitude may have a possible explanation in the fact there was little focus on an appropriate transmission from the vibration source to the productive formation. In fact, considerable attenuation phenomena occur within the rock matrix between the vibrations transmission point and the target area, which is the greater formation volume situated beyond the immediate proximity of the well casing. Prior art explored the use of vibrations to stimulate the crude oil influx wherein said vibrations are transmitted to the rock matrix from (a) the Earth's surface, (b) through the well casing wall or (c) through perforations in the well casing.

Stimulation methods based on vibrations transmitted from the Earth's surface, through the soil, may be effective only for shallow reservoirs and require extreme amplitudes that are destructive for the oilfield equipment in absence of features countering the attenuation phenomena which are maximal at the Earth's surface, where the top soil has the least compaction.

The downhole vibration transmission to the rock through either the casing wall or the casing perforations is limited, by definition, because the casing itself is a physical barrier. Moreover, a production well casing needs to be protected from the negative effects of long term vibration exposure.

Despite being generated or transmitted at downhole level, fluid driven processes have their effects limited by the casing perforations' size. Moreover, fluids dissipate in an uncontrollable manner within the rock matrix once exiting the perforations, requiring large quantities to obtain a sizeable effect. Subsequent production must lift back a considerable part of the injected liquid, with additional treatment costs and related greenhouse gases (GHG) emissions.

While able to release a considerable amount of energy at downhole level, explosive based methods are uncontrollable and destructive for the well construction.

An economically quantifiable stimulation effect can be triggered by a critical amount of energy reaching the greater formation volume situated beyond the immediate proximity of a production well casing. Therefore, in order to achieve this result, a vibratory process must be able to generate a high amount of energy at a downhole level and to transmit it to the target with minimal attenuation.

Features or combination of features as: generation of strong vibrations at a level close to the formation level as emitted by a downhole vibration source able to generate such vibrations or as transmitted downhole with minimal attenuation, if generated by a vibration source able to generate such vibrations (i.e., high peak force mechanical vibrator) located at a different level or at the Earth's surface; transmission of vibrations to the rock, with minimal attenuation, from the exterior of the well casing at downhole level, bypassing the said casing; in-situ amplification for the vibration transmission; have the ability to: deliver a high amount of energy at a level close to the formation level, and/or transmit this energy to the appropriate formation area while overcoming attenuation in order to release upon the target the critical amount of energy necessary to stimulate the formation as to obtain a production enhancement.

Toughness is a material characteristic of prime importance in the vibration transmission. The rock is generally a brittle medium, which made possible the fracking stimulation paradigm. For the vibration stimulation typology, the medium brittleness is a major setback which needs to be properly addressed, because (a) the brittleness per se is an attenuation factor, as a brittle medium fracks under stress and (b) as a consequence of historical stress, the rock medium is naturally fractured, making possible relative movement within its volume, with associated attenuation.

Relative toughness, well known in materials science, and calculable in a manner well known in materials science, is the factor which differentiates the vibration transmission quality. Not only does a tougher medium better withstand the vibrational energy in a long term repetitive scenario since it develops fewer or smaller fractures over time, but, due to the same reason, vibrations are less attenuated within such a medium, in the same long term scenario.

For soft or relatively elastic rocks, like oil sands, clay or top soil, vibrations are less attenuated within a medium with a greater strength than the rock, the relative strength being the factor which differentiates the vibration transmission quality in this case.

A composite material—such as one resulted from a combination between the rock and a binding or tackifying agent, such as a resin—has an increased toughness compared to its higher brittleness component, the most usual example being laminated glass. Such a composite material also has an increased strength compared to its softer component, and is therefore suited to withstand vibrations and counter attenuation in both cases.

In the vibration transmission, the transverse sections of the transmission chain components, as compared to the vibration direction (sections perpendicular to the force generated by the vibration source), are the active sections which determine the active coupling. A greater active section area of the transmission component in contact with the rock makes the vibrations to be applied to the rock from a greater surface, as a kind of geometrically determined in-situ amplification for the vibration transmission.

Reinforcing an element whose purpose is to transmit vibrations with a high-toughness reinforcement, such as a metallic part, improves the vibration transmission quality in a long term repetitive scenario. A better spatial distribution of the reinforcement, such as one obtained by using a deployable reinforcement, further improves the quality of the vibration transmission.

Unlike a fracking process, which develops the fractures matrix created by previous operations, a vibratory process has the ability to dynamically change the rock matrix. This particularity makes certain beneficial effects—like altering water fingers in order to decrease watercut—to be unrelated to previous applications, especially because vibration control allows different application scenarios. This long-term efficiency justifies permanently installed process-dedicated equipment, permanent alterations to the well casing or even process-dedicated wells.

Transforming a permanently closed well, or one selected to be permanently closed, into a well dedicated to a vibratory process extends the utilization lifetime of that well.

As a metallic tube, the casing allows vibration transmission along its axis with minimal attenuation, therefore a well casing can be used as a transmission link between the vibration source and the transmission point to the rock.

If used alone, enhanced oil recovery (EOR) processes, such as thermal methods, limit their effects to a certain volume of the productive strata, the stimulated area, located around the injection agent main paths, where the hydrocarbons' viscosity is decreased sufficiently to flow freely within the rock matrix. Within a quasi-stimulated area located between the stimulated area and the cold area, the said viscosity has a value in a range which prevents free flow, but is decreased enough, as an effect of the thermal method, for the application of an external force, such as one emerged from a vibratory process, to generate and maintain crude oil flow from the quasi-stimulated area towards the well bore. This particularity makes the use of a process-dedicated well to be particularly beneficial as it stimulates with priority the quasi-stimulated areas of nearby wells submitted to a thermal EOR processes.

Notation 1. In the last part of a cyclic steam stimulation (CSS) or when the parameters (steam quantity or temperature) of a continuous steam injection are decreased, the stimulated area diminishes and retracts closer to the main fluid paths. As a consequence, the quasi-stimulated areas migrate, approaching the main fluid paths and the production well bore. This phenomenon makes the application of a vibratory process to be particularly effective in these situations as less attenuation needs to be countered. Such a situation can be sensed at the surface using as reference the moment when the produced oil viscosity exceeds a preset value. If applied so, a vibratory process can be used also to increase the production phase of a cyclic steam injection, therefore decreasing steam injection frequency, or to decrease the injection parameters of a continuous steam injection, obtaining a better steam-oil-ratio (SOR) in both cases. This specific application is particularly beneficial not only for heavy oil production in areas where water supply is problematic (Middle East) or where steam production and transport is extremely costly due to climate (Canada), but also as a way to decrease the GHG emissions related to steam injection.

Notation 2. As a vibratory process dynamically changes the rock matrix configuration by blocking some existing micro paths and opening new ones, therefore enabling a better steam diffusion within the matrix, the use of a vibratory process in the steam injection phase of a CSS, or increasing the steam parameters just before or within the application of a vibratory process in a continuous steam stimulation, lead to a better overall stimulation effect with subsequent lower SOR and GHG emissions.

As the vibratory process improves the oil flow within the productive formation, a production enhancement can be obtained from the combination of the vibratory process with gravity drainage.

For very shallow productive strata, such as oil sands at the boundary area between mining and in-situ production, strong vibrations transmitted from the exterior of a production well casing through the soil combined with an amplification for the said transmission, or gravity drainage or other EOR processes, have the ability to generate an oil flow stimulation up to be considered a production enhancement.

The use of a specific pattern that increases the overall uniformity of the vibratory process effect, such as a plurality of process dedicated wells aligned over the horizontal section of a production well, or one obtained by space partitions as the Voronoi diagram, further enhances the stimulation effect.

Vibration proof construction of the wells, oil lifting equipment and surface related equipment minimizes the negative effects of a long-term vibratory regime over the well or related lifting equipment.

Vibration proof construction of an oilfield, such as one obtained using damping areas between vibratory process-dedicated wells and production wells minimizes the negative effects of a long-term vibratory regime over the production wells or their lifting equipment.

U.S. Pat. No. 2,700,422 (the 422 patent), considered by the inventors to be the closest prior art, while disclosing an embodiment with the vibration source located at the Earth's surface to be used in an abandoned well or earth bore and not to be used as a producing well, describes a body of cement filled in the well bore around the lower portion of an elastic column.

The 422 patent describes the cement body as heavy—the weight being considered a factor which counters the inertia—but it does not take into consideration the relative toughness, compared to the rock, as a vibration transmission factor, the cement being also a brittle medium, unable to withstand vibrations in a long term repetitive scenario. Also, the 422 patent does not take into consideration the geometry of the said body volume in regard to the active contact to the rock, only describing a body of cement filled in the well bore with a large contact surface for a good coupling.

Terms

The term “vibrations” as used herein refers to waves with frequencies in the seismic (infrasonic), sonic or ultrasonic range.

“Vibration proof” construction refers to the construction of a component, whether it is surface equipment, oil lifting equipment, or the like. A component that has vibration proof construction is resistant to the ill effects of long term exposure to vibrations. Use of the term, “vibration proof” in connection with the construction of a component is not intended to mean that the component cannot vibrate.

The terms indicating relative positions compared to given elements, like “below” or “downward” are used in the description to clarify in detail configurations or relative movements with the reference well presumed vertical, if not stated otherwise, such as being compared to the vibrations direction. However, when used in deviated or horizontal wells, these terms refer to the appropriate spatial relationship between the described elements. These terms do not require immediate adjacency between the elements, and accommodate the concept of other elements being present between the described elements, unless otherwise stated.

“Productive formation” refers to any formation below the Earth's surface whether or not the formation is actually productive, is potentially productive, is formerly productive, or is targeted for production.

The term “active section” refers to a section that is perpendicular on the vibration direction (perpendicular on the direction of the force generated by the vibration source).

“In communication with” a formation refers to a relationship between a production well and a productive formation, and means that the production well is positioned to receive withdrawable material from the productive formation. The term does not require that the material be immediately withdrawable but also includes the concept that, if the vibrations are applied, some withdrawable material from the productive formation may move to the production well for eventual withdrawal.

SUMMARY OF THE INVENTION

It is an object of the present invention to wholly or partially overcome the disadvantages of prior art by providing improved systems and methods for stimulating crude oil production from a reservoir. The systems described herein generate vibrations—including strong and very strong vibrations—and enable their transmission to the rock from the exterior of the production well casing with minimal attenuation, combined with a transmission amplification while the transmission chain bypasses the said casing, in order to counter the attenuation phenomena occurring between the transmission point and the formation volume situated beyond the immediate proximity of the well casing.

Aspect 1. Two systems in accordance with the inventive concept include a well, a productive formation, a vibration source and a solid base located between the vibration source and the rock, below the vibration source as compared to the vibrations direction, acting as a hammerhead-like vibration transmission point to the rock matrix.

In these two systems, the vibration source has a downhole vibrating part introduced through the well casing, the base is located downhole, the base has a part in contact with the downhole vibrating part, the downhole vibrating part and the base vibrate freely relative to the well casing, the base has at least a part located in the exterior of the well casing, the base part located in the exterior of the well casing has a part in contact with the rock, and the base has a greater toughness than the rock in contact with it. In the area where the base is in contact with the rock, the base has at least one active section area exceeding the active section area of the base part in contact with the vibration source.

Aspect 2. In the first system, the well component of the system as per Aspect 1, where the vibration source vibrating part is introduced in, is a production well that produces from the formation component of the system and the system stimulates the oil flow from the said formation to the production well component of the system.

Aspect 3. In the second system, the well component of the system as per Aspect 1, where the vibration source vibrating part is introduced in, is a process dedicated well and the system comprises also at least one production well and at least one productive formation, stimulating the oil flow from at least one productive formation to at least one production well component of the system.

In the embodiments as described at Aspect 2 and Aspect 3, the vibration transmission to the rock bypasses the production well casing.

In the embodiments as described at Aspect 2 and Aspect 3, the vibration transmission to the rock is realized from the exterior of the production well, from the base, a tougher element than the surrounding medium.

In the embodiments as described at Aspect 2 and Aspect 3 the base active contact surface to the rock exceeds the active contact surface between the vibration source and the base. As the base is a also tougher medium than the surrounding medium, this feature makes the base to act as a downhole transmitter which provides an in-situ amplification for the vibration transmission to the formation.

In the embodiments as described at Aspect 2, and, respectively, at Aspect 3, the vibration transmission and the related transmission amplification apply to the productive formation component of the system, countering the attenuation phenomena in order to enable the vibratory process to generate a sizeable oil flow stimulation effect.

A process dedicated well is a well entirely dedicated to the vibratory process, especially drilled for or transformed out of an existing well, an active well or, preferably, a closed well or a well awaiting closure.

In a third system, wherein the vibratory process is also applied from at least one process dedicated well, the casing of the dedicated well is used as a transmission link between the vibration source and the base. In this embodiment, both the vibration source vibrating part and the base are in permanent and rigid contact with the casing, being coupled to it, the vibrating part being placed at a higher level or at the Earth's surface. As the casing acts as a downhole protuberance for the vibration source, therefore the vibrations are transmitted along the casing axis, in order to realize the in situ amplification for the vibration transmission, the base has the transverse section area exceeding the transverse section area of the casing. If the interior of the well casing is cemented or filled with a material able to transmit vibrations with low attenuation, such as, preferably, the same anchoring material as used for the base, or a polymer, hybrid mortar or other resin, in order to realize the in situ amplification for the vibration transmission, the base has the transverse section area exceeding the transverse section area of the cylinder having as radius the outer diameter of the casing. In this embodiment in which the casing is used for vibrations transmission along its axis, the said casing may have a plurality of walls or at least one longitudinal rib or reinforcement that increase its ability to withstand strong vibrations in a long term scenario. According to some embodiments, the system includes a plurality of casings with a single base or independent bases, activated by at least one vibration source.

According to some embodiments, the vibration source is controlled. According to some embodiments, the vibration source is an apparatus introduced through the well casing and set at downhole level with the vibrating part placed over the base or coupled to the base. According to some embodiments, the vibration source has the vibrations generator placed at a higher level in the well or at the Earth's surface, being mechanically, hydraulically or pneumatically connected with the downhole vibrating part using connectors, such as rods, tubing or cables. If placed at the Earth's surface level, the vibration source can be a mobile equipment or part of a mobile equipment. If a tube is used for vibrations transmission along its axis, the tube may have a plurality of walls or at least a longitudinal rib or reinforcement that increase its ability to withstand strong vibrations in a long term scenario.

According to some embodiments, the base is located at a level within 100 meters or, preferably, within 50 meters or, even more preferably, within 20 meters from the formation boundary levels. According to some embodiments, the base has at least a part placed below the well casing bottom. According to some embodiments, the area of the active section of the base in contact to the rock exceeds several times the area of the active section of the base on contact with the vibration source.

According to some embodiments, the base is a tool introduced through the well casing. According to some embodiments, the base is a part of the vibration source. The base can also include a loose section of the well casing. According to some embodiments, the base is created through the casing perforations or contains parts introduced or created through the casing perforations.

Aspect 4. According to some embodiments, the base includes a plurality of wires. According to some embodiments, the base includes at least one deployable part which deploys into the rock. According to some embodiments, the deployable part extends or expands laterally as compared to the vibrations direction. The deployment of the said deployable part can be automatic, activated (a) by the downward movement when the part reaches the area beyond the well casing, (b) by an initial elastic load or (c) pneumatically, electrically or mechanically. Shocks or pressure waves may also be used to deploy the said part into the rock. According to some embodiments, the base or the base deployable part drill their path in the rock matrix. According to some embodiments, the deployable part locks in deployed position via a self-locking configuration or using a locking mechanism.

According to some embodiments, the base is connected to the well casing using at least a coupling which allows relative motion between the base and the well casing on the direction parallel to the vibration direction. Moreover, the vibration source can be connected to the well casing using such a coupling. According to some embodiments, the base is connected to the well casing via a packer.

According to some embodiments, the base is composed of or includes a composite material volume, as resulted from a rock toughening or rock consolidation operation, such as a binding or tackifying agent injection, preferably a high bond anchoring resin, such as an epoxy resin. Polymers, cements with increased toughness, such as hybrid mortars or processed via an ion exchange process or other anchoring materials may be also used. The injection operation ensures a large and complex active surface of the composite volume and, according to some embodiments, the injection operation is performed under high pressure, ensuring an even larger surface and more complex shape of the composite volume, for a better active contact with the rock. For certain types of subterranean strata made of soft rocks, such as oil sands, or highly fractured or unconsolidated strata, the base is a composite material volume with greater strength than the subterranean medium in contact with the base, as resulted from the said rock consolidation operation.

According to some embodiments, the base is composed of or includes a reinforced composite material volume which includes at least a reinforcement. According to some embodiments, the reinforcement is a part introduced and set into desired position through the well casing. According to some embodiments, the reinforcement is provided with at least one interior hole and at least one perforation and also serves as injector for the rock toughening or consolidation operation, subsequently remaining embedded in the composite material volume, reinforcing it. According to some embodiments, the reinforcement is a deployable structure or includes at least a deployable part, as described within.

Aspect 4. According to some embodiments, the said deployable part is provided with at least one interior hole connected to the reinforcement hole and at least one perforation, acting also as an injection point for the rock toughening or consolidation operation. An injection operation performed from multiple points spread beyond the wellbore boundary ensures a better spatial distribution of the higher toughness component of the composite volume, such as the high bond resin, improving both the volume, the configuration and the material quality of the active section of the base.

According to some embodiments, the rock toughening or consolidation operation is realized or repeated through the reinforcement. According to some embodiments, the rock toughening or consolidation operation is realized or repeated through the space between the reinforcement and the well casing. According to some embodiments, the rock toughening or consolidation operation is realized or repeated using a packer.

According to some embodiments, the well bottom is opened prior to the introduction or creation of the base. According to some embodiments, the rock is fractured in the base area before or during the creation of the base. According to some embodiments, a cavern is created in the base area before or during the creation of the base. According to some embodiments, new perforations or slots are created prior to the creation of the base. According to some embodiments, the base is realized sequentially, out of a sequential deployment or creation of its components.

As the bottom of a production well is filled with liquid, such as crude oil, which acts as a powerful damper for the vibration transmission on any direction, at least one component of a vibratory system whose vibrations transmission chain is located or activated in a production well can be provided with a gas or foam source which generates a gas or foam flow below the liquid level in the production well casing, minimizing the said damping effect. According to some embodiments, the gas or foam source is autonomous. According to some embodiments, the gas source is the exhaust of a pneumatic activation device of the vibration source.

Aspect 5 Another system according to the invention comprises at least a production well that produces from a formation located at 50-250 m below the Earth's surface, a high peak force mobile vibration source and a solid base acting as vibration transmission point to the soil wherein the mobile vibration source has the vibrating part placed over the base, in contact with the base, the base is located in the exterior of the well casing, the base has at least a part located underground, in contact with the soil, the base has a greater toughness than the soil in contact with it, the base part in contact with the soil has a transverse section area exceeding the transverse section area of the vibrating part in contact with the base, the mobile vibration source generates vibrations with a peak force in excess of 50 kN or, preferably, in excess of 100 kN.

Aspect 6. According to an embodiment for the system described at Aspect 5, the base is located below the Earth's surface. According to another embodiment for the same system, the mobile vibration source is located below the Earth's surface. According to some embodiments, the base has at least one protuberance which extends from the base towards the formation.

According to some embodiments, the systems are used in combination with other IOR/EOR methods such as water or solvents injection, steam injection etc.

According to some embodiments, the systems are used in combination with gravity drainage as a “Vibration Assisted Gravity Drainage” (VAGD), with the base within or above the productive formation. If using a process dedicated well, the base is set above the horizontal part of the production well or lateral to it.

According to some embodiments, the VAGD is used in combination with other enhancement methods related to gravity drainage, such as SAGD or VAPEX.

According to some embodiments, the vibration process and the steam injection process are used in a cyclic combination wherein the vibratory process is started within the injection phase of a cyclic steam stimulation (CSS) or the steam parameters of a continuous steam injection, including SAGD, are briefly increased before or at the start of the vibratory process and decreased in (a) the last part, (b) at the end or (c) immediately after the vibratory process, for a better diffusion of the steam within the formation. This combination is able to increase the steam injection efficiency, with the subsequent decrease of the overall SOR and GHG emissions out of the reasons described at Notation 2.

According to some embodiments, the vibration process and the CSS are used in another cyclic combination wherein the vibratory process is started when the produced oil cinematic viscosity exceeds a value which (a) depends upon local geology parameters such as porosity and permeability or (b) is empirically calibrated on site or (c) increases above a general reference value, such as 50 cP for low permeability strata and 100 cP for high permeability strata. According to some embodiments, the vibration process and the continuous steam injection processes, including SAGD, are used in a cyclic combination wherein the steam parameters, such as steam quantity and steam temperature, are decreased (a) before, (b) at the start or (c) within the vibratory process and restored (a) before, (b) at the end or (c) briefly after the end of the vibratory process, also increasing the process efficiency and subsequently decreasing the SOR and GHG emissions out of the reasons described at Notation 1.

According to some embodiments, the VAGD comprises a plurality of process dedicated wells aligned on a line that is parallel to the horizontal part of a production well, over it or lateral, between the horizontal sections of two production wells.

According to some embodiments, the VAGD comprises a plurality of process dedicated wells, the vibration source is at least a mobile equipment and the vibratory process is applied sequentially to the plurality of wells, preferably along the said line of wells, from the mobile vibration source. According to some embodiments, the system comprises a plurality of stationary vibration sources activated concomitantly or sequentially.

According to some embodiments, the vibrations parameters, including amplitude and frequency, of a vibratory process applied as per the present invention are calibrated according to the characteristics of the targeted area within the formation, including resonant frequency.

According to some embodiments, at least a well component of the systems has a vibration proof construction, such as one using casing isolation, use of flexible joints, snubbers, shock absorbers, vibration proof fasteners, springs or damping fluids.

According to some embodiments the oil lifting and related surface equipment have a vibration proof construction, such as one obtained by using tubing and pump dampers, flexible connections, snubbers, shock absorbers, vibration proof fasteners which further minimize the negative effects of a long-term vibratory regime over the oil lifting equipment and the surface equipment.

According to some embodiments, seismic tests are used to set the location of a process dedicated well, or to monitor or guide the vibratory processes applied as per the present invention.

As the stimulation effects of high or extreme amplitude vibratory processes, technically possible according to the present invention, are less dependent upon reservoir parameters, such as local porosity and permeability, than those generated by lower amplitude processes, a space partition like the Voronoi diagram is able to ensure a more uniform application of the process at oilfield scale. According to some embodiments, the dedicated wells or bases locations are set at the intersection points of the Voronoi diagram lines having as generator points the production wells or, depending on site conditions, within the circles having as center the intersection points of the said Voronoi diagram and having as radius ½ of the distance between the said centers and the production wells location.

According to some embodiments, if using vibratory process dedicated wells or zones, the oilfield has a vibration proof construction, obtained using damping or isolation areas such as trenches between the vibratory process wells or zones and the production wells.

While the description herein contains many features, these features should not be construed as limitations on the scope of the disclosure or of the appended claims. The features described in the context of separate embodiments can also be implemented in combination. Conversely, various features described in the context of a single exemplary embodiment can also be implemented in multiple exemplary embodiments separately or in any suitable partial combination.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 depicts an embodiment in which the well component of the system is a process dedicated well.

FIG. 2 depicts another embodiment in which the well component of the system is a process dedicated well. In this example, the casing of the process dedicated well component of the system is the transmission link between the vibration source and the base.

FIG. 3 depicts another embodiment in which the well component of the system is a process dedicated well. In this example, the casing of the process dedicated well component of the system is the transmission link between the vibration source and the base.

FIG. 3a depicts a variation of the embodiment depicted in FIG. 3. In this example, the casing of the process dedicated well component of the system is the transmission link between the vibration source and the base.

FIG. 3b depicts a variation of the embodiment depicted in FIG. 3. In this example, the casing of the process dedicated well component of the system is the transmission link between the vibration source and the base.

FIG. 4 depicts an embodiment in which the well component of the system is a production well.

FIG. 5 depicts an embodiment in which the well component of the system is a production well.

FIG. 6 depicts an embodiment according to Aspect 5 or Aspect 6, mentioned above.

FIG. 6a depicts a variation of the embodiment according to Aspect 5 or Aspect 6, mentioned above.

FIG. 7 shows a pattern using well pattern using a Voronoi diagram for the location of a process dedicated well in relation to the production wells' locations according to an embodiment.

DETAILED DESCRIPTION

FIG. 1 shows a system 100 according to the invention comprising (1) a well 101, drilled for the vibratory process, having the casing 102, (2) a productive formation 104, (3) a production well 103 that produces from the formation 104, (4) a vibration source 105 placed downhole and activated from the surface and (5) a base 106 which is a metallic tool introduced through the casing 102 and is composed of the head 107 and the lower part 108. The vibration source 105 is placed over and coupled to the head 107 of the base 106.

The base 106 part 108 drills its path laterally in the rock below the well bottom 109 which is located above the formation 104, then is locked in position using a locking mechanism, not represented, when reaching the desired position, increasing the active surface in contact with the rock, the area of the transverse section b-b of the base 106 part 108 in contact with the rock exceeding the area of the transverse section a-a of the base 106 part 107 in contact with the vibration source 105. As the vibration source 105 generates the vertical vibrations 110, the transverse sections a-a and b-b are active sections.

The base 106 head 107 is connected to the casing using the packer 111 which allows relative vertical motion between the base 106 head 107 and the casing 102, the relative motion being parallel to the vibration direction. An example of a connection allowing the said relative vertical motion is illustrated in the detail 100 a, via the buffer zones 112 and 113 created between the channel 114 of the packer 111 and the shoulder 115 of the head 107.

The vertical vibrations 110 generated by the vibration source 105 are transmitted to the formation 104 from the exterior of the casing 102 through the base 106 and the elastic waves 116, stimulating the oil flow 117 within the formation 104 towards the production well 103, therefore bypassing the casing 102. As the base 106 is connected to the casing via the packer 111 which allows relative vertical motion between the base 106 and the casing 102, the system vibrates freely relative to the casing 102, minimizing attenuation that could be caused by a rigid contact to the casing 102 and protecting the casing 102 from the negative effects of long term vibration exposure.

The fact the vibratory process is generated and transmitted from the dedicated well 101 allows the production well 103 to be continuously equipped with oil lifting equipment. The well 103, the downhole pump 118, the tubing 119 and surface driving unit 120 have a vibration proof construction by using the damping anchors 121 between the tubing 119 and the well 103 casing 122 and by using the flexible joint 123 between the well 103 casing flange 124 and the flange 125 of the driving unit 120.

As the tubular shape of the vertical casing 102 allows vertical vibrations of any amplitude to be generated or transmitted in the interior of the casing 102, combined with the fact the casing 102 is separated, for vertical vibrations, from the vibration transmission chain by the packer 111, the system 100 allows the safe transmission of strong and very strong vertical vibrations.

The construction of the base 106, out of a metallic tool provided with a locking mechanism, enables it to be run out of the well if desired. A system like 100, using a removable base run in a dedicated well which vibrates freely relative to the dedicated well casing, allows the dedicated well to be reused in future for other applications such as production or other stimulation typologies.

FIG. 2 shows a system 200 according to the invention belonging to the typology with the well casing being the transmission link between the vibration source and the base as per the “third system”, the system 200 being a special decommissioning of a production well, comprising (1) a well 201, having the casing 202, (2) a productive formation 203, (3) a vibration source 204 located at the Earth's surface, (4) a base 205 located downhole at the casing 203 perforations 206 level and (5) a production well 207.

The well 201 is transformed into a vibratory process dedicated well out of a closed well that was producing from the formation 202.

The well 201 is located between several production wells that produce from the same formation 202 and are submitted to a cyclic steam injection process, exemplified by the production well 207. As a result, the formation is split into a stimulated area 208, located within the formation 203 mainly next to the well 207 casing 209, a quasi-stimulated area 210 located mainly beyond the stimulated area 208 as compared to the casing 209 and a cold area 211.

The vibration source 204 is a mobile high peak force vibrator, such as a seismic vibrator, and is in contact with the well 201 casing 203 via its vibrating part 212 placed over the top of the well 201 over a platform 213, coupled to the flange 214 of the casing 203 and further rigidly connected to the casing 202 through the beams 215 and the concrete volume 216.

The base 205 is located at the perforations 206 level, with a part 217 within the casing 203 and the perforations 206 and a part 218 in the exterior of the casing 203. The part 218 of the base 205 located in the exterior of the casing 203 is a composite material volume with a greater toughness than the surrounding medium as the base 205 is the result of a high pressure injection of a high bond resin, which realizes a rock toughening operation in the exterior of the well 201 casing 203, as the main fluid paths within the formation 202 located next to the casing 203 and at least a part of the fractures matrix of the brittle rock medium from the same area are filled with the binding agent, the resulting composite volume being a tougher medium than the surrounding rock in the same way laminated glass is a tougher material than regular glass. The binding agent also binds the well casing to the composite material volume, whose transverse section exceeds the transverse section of the cylinder having as radius the external diameter of the casing 203, realizing the in situ amplification for the vibration transmission.

The volume 219 from the well 201 bottom 220 to the base 205 and the volume 221 from the base 205 to the well top flange 214 are cemented with a polymer enhanced cement or, preferably, with the same high bond resin as the base 205.

The vertical vibrations 222 emitted by the vibrating part 212 of the vibration source 204 are transmitted, via the platform 213, the flange 214, the beams 215, the concrete volume 216, the casing 202, the cemented volume 221 and the base 205 to the formation 202 as the quasi-radial elastic waves 223 which, in their horizontal part 224 are propagating within the formation 202, particularly effective in stimulating the oil influx 225, first from the quasi stimulated area 210, then from the stimulated area 208 to the well 207 perforations 226.

The system is started periodically, in the last part of the production phase of the cyclic steam stimulation performed at the well 207, when the cinematic viscosity of the oil produced by the well 207 increases above 50 cP for low permeability strata or above 100 cP for high permeability strata.

Between the well 201 and the well 207, the trench 227 has the role of a buffer area, protecting the well 207 construction, its oil lifting equipment and related surface equipment from the negative effects of long term vibration exposure, especially as the system operates with high amplitude vibrations, generated by the vibration source 204.

FIG. 3 shows a system 300 according to the invention, also belonging to the typology with the well casing being the transmission link between the vibration source and the base, as per the “third system”. The system, 300, is a “Vibration Assisted Gravity Drainage” (VAGD) which can be used alone or, as represented herein, in combination with steam assisted gravity drainage (SAGD) in softer rocks like oil sands and comprises (1) a well 301, having the casing 302, (2) a productive formation 303, (3) a vibration source 304, which, similarly to 200, is a mobile high peak force vibrator, with the vibrating part 305 in contact with the well 301 in an identical way as in the system 200, (4) the base 306 and (5) the production well 307.

The well 301 is specially drilled for the vibratory process with the well bottom 308 above the formation 303.

The base 306 is a reinforced composite material volume composed of the reinforcement 309 and the composite material volume 310.

The reinforcement 309 is a metallic tool introduced through the well casing with the tubing 311, then rigidly connected to the casing 302 via the packer 312, with a part 313 in the exterior of the well 301 casing 302, in the area below the well 301 bottom 308. The reinforcement 309 part 313 is provided with the deployable parts 314 which, given the softer nature of the rock, deploy automatically due to their lower end shape 315 when the part 313 reaches the area below the well bottom, then lock into the deployed position via a locking mechanism, not represented. Both the part 313 and the deployable parts 314 are hollow and are provided with the perforations 316, these perforations serving as injection points for the injection operation which creates the composite material volume 310.

The composite material volume 310 is the result of a pressure injection of a binding agent such as a high bond resin via the perforations 316 in a similar way as described for the system 200. In this case, given the softer nature of the rock, the binding agent injection operation realizes both a strengthening and toughening rock operation.

The deployment of the reinforcement 309 realizes both a better spatial distribution for the injection operation and a better spatial distribution of the reinforcement, as the part 313 and the deployable parts 314 rest embedded in the composite volume, reinforcing it. The deployment of the reinforcement 309 and the subsequent injection operation also ensures at least one transverse section of the base 306 in contact with the rock to exceed the transverse section having as radius the outer radius of the casing 302, realizing the in situ transmission amplification.

The well 301 casing 302 is filled with recycled polymer, with the tubing 311 embedded in the volume 317, therefore reinforcing it for a better, less attenuated, vibration transmission from the vibration source 304 to the base 306. The recycled polymer withstands vibrational energy in a long term repetitive scenario while being easy to be removed for future access to the base 306 in order to repeat the injection operation, if necessary.

The production well 307 is a horizontal well and the formation 303 is submitted to a steam assisted gravity drainage process being crossed, in the area below the base 306, by the horizontal section 318 of a steam injection well 319, shown in FIG. 3a , and the horizontal section 320 of the production well 307.

The vertical vibrations, not represented, emitted by the vibration source 304 are transmitted to the formation 303, from the base 306 with minimal attenuation and benefiting from the in situ transmission amplification, as the radial waves 321 that enhance the stimulation effect of the SAGD process, improving the oil drainage 322 to the production well 307.

FIG. 3a shows a vibration assisted gravity drainage system where a plurality of process dedicated wells 301, as per 300, as “Hammer Wells” are drilled in a line with the bases 306 above the horizontal section 318 of the steam injection well 319 and the horizontal section 320 of the production well 307 and the vibration source 304 activates sequentially the vibratory process.

FIG. 3b shows a base 306 created sequentially via directional drilling and sequential introduction of two reinforcements 323 prior to the binding agent injection which fills the boreholes. Such a base can also be created by converting a multilateral well, such as a steam injection well component of a SAGD application, into a process dedicated well.

FIG. 3b also shows a construction which uses casing isolation, further countering attenuation and protecting nearby oilfield equipment. In this case, the casing 302 is isolated from the soil at the Earth's surface level, an area of maximal attenuation, by the conductor pipe 324. The platform 325, in contact with the vibrating part 305 is isolated from the concrete volume 326 which is rigidly connected to the conductor pipe 324, so the system vibrates freely relative to the assembly composed of the conductor pipe 324 and the concrete volume 326, assembly embedded in the soil.

FIG. 4 shows a system 400 according to the invention belonging to the typology where the well component of the system is a production well, comprising the well 401, the formation 402, the vibration source 403 and the base 404.

The well 401 is a production well, having the casing 405, the perforations 406 and the well bottom 407 and produces from the formation 402.

The vibration source 403 is composed of (a) the mechanical vibrator 408 located the Earth's surface on the mobile equipment 409, (b) the downhole vibrating part which, in this case, is the weight 410, introduced through the well 401 casing 405 and placed over the base 404, and (c) the cable 411 which couples the vibrator 407 and the weight 409.

The base 404 is a reinforced composite material volume composed of the reinforcement 412 and the composite material volume 413, located in the exterior of the well 401 casing 405.

The reinforcement 412 is composed of the head 414 and the lower part 415, located in the exterior of the well casing, below the well 401 bottom 407, both the head 414 and the lower part 415 being hollow. The lower part 415 is provided with the perforations 416 and the deployable part 417 composed of several mechanisms 418 which, deploy through an upward drilling movement when reaching the area below the well bottom 407 and create the cavern 419 prior to the rock consolidation operation that creates the composite material volume 413, composed of a binding agent injection. The reinforcement deployment and the rock consolidation operation are presented sequentially in the FIG. 4a . Such a typology for the reinforcement offers the advantage of a controlled deployment. In this case, the rock consolidation operation is a mix of rock strengthening for the cavern area and rock toughening for the area adjacent to the cavern. The deployable part 417 rests deployed during the rock consolidation operation, becoming permanently embedded in the strengthened volume, further increasing the quality of the vibrations transmission through the base 404.

The weight 410 is placed over the head 414 of the reinforcement 412, the contact between the weight 410 and the head 414 being realized through the spring 420 and the mobile plate 421. The assembly composed by the spring 420 and the mobile plate 421 has multiple functions: (a) to realize a permanent contact between the weight 410 and the head 414 during the vibratory process, given the fact the weight 410 is placed over the head 414 and not rigidly coupled to it, (b) to protect the head 414 from long term negative effects of chokes exposure and (c) to realize a mechanical buffer which allows the mechanical vibrator to have a tolerance while generating vibrations that offset the cable 411 elongation.

As the bottom of the production well 401 is filled with crude oil up to the static level 422, the weight 410 is provided with the autonomous foam source 423 which generates a foam stream, therefore countering the dampening effect of the downhole liquid upon the weight 410 while the weight 410 is vibrating.

The head 414 is coupled to the casing 405 via the packer 424 which allows relative vertical motion between the head 414 and the casing 405.

The horizontal vibrations generated by the vibrator 408 are transmitted to the weight 410, as the vertical vibrations 425 then to the base 404 reinforcement 412 head 414 via the spring 420 and the mobile plate 421 and from the base 404 composite material volume 413 located in the exterior of the well casing to the rock towards the formation 402 as the quasi-radial waves 426, stimulating the oil flow from the formation 402 to the well 401 perforations.

This construction allows the rock consolidation operation to be repeated through the reinforcement 412 or, using the packer 424, through the annular space between the casing 405 and the lower part of the reinforcement 412 head 414.

FIG. 5 shows a system 500 according to the invention belonging also to the typology where the well component of the system is a production well, to be used in production wells whose bottom is located far from the productive formation.

The system 500 is composed of the production well 501 having the casing 502, a vibration source 503 located below the well 501 perforations 504 level, a productive formation 505 and a base 506.

The well 501 producing from the formation 505 and has the well bottom far from the formation 505 level.

The base 506 is composed of (1) a tube 507, introduced through the well 501 casing 502 and provided with the perforations 508, (2) the segment 509 separated from the casing 502 below the perforations 504 at a level close to the formation 505 level and provided with the slots 510, (3) the packers 511 and 512 which rigidly connects the tube 507 and the segment 508 and (4) a composite material volume 513 resulted from a binding agent injection through the perforations 508 and the slots 509.

The vibration source 503 is in contact with the tube 507 and generates the horizontal vibrations 514 perpendicular on the casing 502 axis and on the representation plane.

The area of the active section of the base in contact with the rock, which, in this case, coincides with the composite volume representation area, largely exceeds the active section area of the vibration source in contact with the base which, in this case, is the vibration source representation rectangle.

The base 506 is connected to the casing 502 via the packers 515 and 516 and the connectors 517 and 518 which allow relative horizontal motion, parallel to the vibration direction, between the base 506 and the packers 515 and 516.

The horizontal vibrations 514 are transmitted to the productive formation 505 as the radial waves 519, stimulating the oil influx 520.

The tube 507, the packers 510,511,513 and 514 and the connectors 515 and 516 can be a part of a tool introduced through the casing 502 which mat also include the vibration source 503.

FIG. 6 presents a system 600 according to the invention wherein high amplitude vibration are emitted from the exterior of the well casing towards a shallow formation, comprising (1) a production well 601 submitted to a cyclic steam stimulation, having the well casing 602 and the perforations 603, (2) a formation 604, (3) a vibration source 605 and (4) a base 606.

A cyclic steam stimulation is performed via the production well 601, the system 600, being activated immediately after the soaking phase. As a consequence and similarly to the case presented in the description of the system 200, the formation 604 is split into a stimulated area 607, a quasi-stimulated area 608 and a cold area 609.

The formation 604 is composed of shallow oil sands strata, situated at a depth less than 250 m or, preferably, less than 200 m.

The vibration source 605 is a high peak force seismic vibrator whose applied peak force exceeds 50 kN, or, preferably, 100 kN, generating very strong vertical vibrations.

The base 606 is located underground, as a layer of surface soil, with the least compaction, is previously excavated at the base location, which is over the quasi stimulated area 608 of the formation 604.

The base 606 is composed of a metallic platform 610 whose transverse section area exceeds the area of the vibration source in contact with it, placed over a reinforced concrete volume 611. A trench 612 located on the base perimeter protects the well 601, as well as other wells or related oilfield equipment, from the negative effects of high amplitude vibrations generated by the source 605 on a long term repetitive scenario.

Another trench 613 and a vibration proof construction of the well 601, similar to the one presented in the description of the system 200, further protects the well 601, as well as other wells or related oilfield equipment, from the negative effects of high amplitude vibrations generated by the source 605 on a long term repetitive scenario.

A ramp 614 enables the mobile vibrator to access its working position over the base 606.

The vertical vibrations 615 are transmitted from the base 606 to the formation 604 as the elastic waves 616 improving the oil influx 617 towards the well 601 perforations 603.

The vibration generation and their transmission amplification in the exterior of the well casing, combined, in this case, with (1) the use of high amplitude vibrations from a vibration source located underground, (2) the location of the productive strata relatively close to the Earth's surface, and (3) the effects of a thermal stimulation process, enables the said vibrations to counter the attenuation phenomena, despite the location of the base, which is the vibration transmission point, much closer to the Earth's surface than in all other cases described herein.

Moreover, the system 600 allows the safe transmission of even extreme vibrations, such as the ones emitted by a vibration source with an applied force in excess or 150 kN or, preferably, in excess of 200 kN, or, even more preferably, in excess of 250 kN, able to deliver to the formation the critical energy needed to better counter the attenuation phenomena and to trigger a stimulation effect that results in a sizeable production enhancement. In fact, the system 600 allows the safe and targeted transmission of vibrations of any amplitude, as generated by present and future high peak force vibration sources.

The system 600 becomes a cost effective stimulation process solution for shallow strata that are just too deep to be produced by surface mining, as an intermediary solution—depth wise—between mining and other in-situ stimulation solutions according to the present invention, for example the one enabled by the system 300.

FIG. 6a presents a version of the system 600 composed of plurality of bases 606 aligned over the horizontal section 618 of the production well 601, which is a reaction well for a SAGD system, comprising also the horizontal steam injection well 619. The bases are activated sequentially by the vibration source 604 which is a high peak force mobile vibrator.

FIG. 7 presents a well pattern for a vibratory process application which follows the Voronoi diagram having as generators the production wells 701 locations and the process dedicated wells or bases locations set at the said diagram intersection points 702. 

There is claimed:
 1. A system, comprising: a production well in communication with a productive formation, a vibration source above a rock matrix, configured to introduce vibrations in a vibrations direction, and a solid base between the vibration source and the rock matrix, below the vibration source as compared to the vibrations direction, acting as a vibration transmission point to the rock matrix, wherein the vibration source has a downhole vibrating part disposed within a well casing, wherein the base is located downhole, wherein the base has a part in contact with the downhole vibrating part, an area of said contact between the part of the base and the downhole vibrating part defining a first respective active section area, wherein the downhole vibrating part and the base vibrate freely relative to the well casing, wherein at least a portion of the base is disposed exterior of the well casing, wherein the portion of the base part exterior of the well casing contacts the rock matrix, said contacts defining a contacted part of the rock matrix, an area of said contact between the portion of the base part and the contacted part of the rock matrix defining a second respective active section area, wherein the base has a respective toughness greater than the toughness of the contacted part of the rock matrix, and wherein the second respective active section area exceeds the first respective active section area.
 2. A system according to claim 1 which further includes a vibrations process-dedicated well wherein the vibration source vibrating part is introduced through the process-dedicated well casing.
 3. A system according to claim 1 wherein the base is connected to the well casing using at least a coupling which allows relative motion on the direction parallel to the vibration direction between the base and the well casing.
 4. A system according to claim 1 wherein the vibration source is an apparatus introduced through the well casing and set at downhole level with the vibrating part placed over the base or coupled to the base.
 5. A system according to claim 1 wherein the base includes a loose section of the well casing.
 6. A system according to the claim 2 wherein the vibration source and the base are coupled to the process dedicated well casing and vibrate with it, wherein the vibration source generates vertical vibrations, wherein the base has at least one transverse section area exceeding the transverse section area of the casing.
 7. A system according to the claim 6 wherein the interior of the process dedicated well casing is filled in the area above the base, wherein the base has at least one transverse section area exceeding the transverse section area of the cylinder having as radius the outer diameter of the casing.
 8. A system according to claim 1 wherein the vibration source has the vibrations generator disposed at one of a higher level in the well and at the Earth's surface, and coupled with the downhole vibrating part.
 9. A system according to claim 1 wherein the base is a tool provided with at least a deployable part adapted to extend or expand into the rock in a direction lateral to a direction of the vibrations.
 10. A system according to claim 1 wherein the base is adapted to drill a path in the rock matrix.
 11. A system comprising: a production well in communication with a productive formation, a vibration source, and a solid base acting as a vibration transmission point to the soil; wherein: the productive formation is between 50 m and 250 m below the Earth's surface, the vibration source has a vibrating part over the base, and in contact with the base, the base is located at least in part in the exterior of the well casing, the base has at least a part located underground, in contact with the soil, the base has a respective toughness greater than a respective toughness of the soil in contact with the base, the base part in contact with the soil has a transverse section area exceeding the transverse section area of the vibrating part in contact with the base, the vibration source is adapted to generate vibrations with a peak force in excess of 50 kN.
 12. A system according to claim 1 wherein the vibration source is a controlled vibration source.
 13. A system according to claim 1 wherein the vibration source is a part of a mobile equipment.
 14. A system for stimulating the oil production from a reservoir using vibrations whose vibration transmission to the rock is realized from a composite material volume with a respective toughness greater than the toughness of the rock in contact with the composite material volume, the composite material volume being created from an operation on the rock, including one of a rock toughening operation and a rock consolidation operation.
 15. A system according to the claim 14 wherein the composite material volume has a respective strength greater than a strength of the rock in contact with the composite material volume.
 16. A system according to claim 14 wherein the composite material volume includes a reinforcement.
 17. A system according to claim 16 wherein the reinforcement is introduced through the well casing.
 18. A system according to claim 17 wherein the reinforcement is provided with at least one interior hole, and at least one perforation and serves as injector for the operation on the rock.
 19. A system according to claim 18 wherein the reinforcement is provided with a deployable part adapted to deploy in the rock in a direction lateral to a direction of the vibrations.
 20. A system according to claim 19 wherein the deployable part is provided with at least one interior hole connected to the reinforcement hole, and at least one perforation, acting also as an injection point for the operation on the rock.
 21. A system according to claim 9 wherein the deployable part is adapted to lock in a deployed position.
 22. A system for stimulating oil production using vibrations, comprising a source component, located in a well casing of a production well, below a liquid level of the production well, the source component being adapted to output, in the production well casing, a flow of one of gas and foam, below the liquid level.
 23. A system according to the claim 22 wherein the source component is autonomous.
 24. A system according to the claim 22 wherein the source component is configured to output exhaust of a pneumatic activation device.
 25. A system, intended for use in stimulating oil production, comprising: surface equipment, oil lifting equipment adapted to lift oil to the surface equipment, and a vibration component, adapted to generate vibrations for stimulating the production of the oil; wherein at least one of the oil lifting and the surface equipment have a vibration proof construction, and wherein the vibration proof construction includes one or more of tubing and pump dampers, flexible connections, snubbers, shock absorbers, and vibration proof fasteners.
 26. A method for stimulating the production of oil using vibrations, comprising: providing a plurality of vibration process-dedicated wells aligned over or lateral to a horizontal part of a production well; and sequentially applying a vibration process to the plurality of vibration process-dedicated wells; wherein the sequential application of the vibration process comprises generating vibrations from a vibration source mounted on equipment adapted to be mobile equipment.
 27. A method for stimulating the production of oil using vibrations, comprising: providing a plurality of vibration process-dedicated wells aligned over or lateral to a horizontal part of a production well; applying a vibration process to the plurality of vibration process-dedicated wells; wherein the application of the vibration process comprises generating vibrations from a plurality of vibration sources each dedicated to a respective one of the plurality of vibration-process wells. 